Advances in semiconductor manufacturing technology have resulted in the reduction in size of many circuit elements, including but not limited to transistors. In turn, these reductions in the physical dimensions of various circuit elements and interconnections has provided the capability to cost-effectively include very large numbers of interconnected circuit elements on integrated circuits, or chips. This capability has enabled the practical implementation of complex signal processing in the digital domain.
With the ability to cost-effectively implement digital signal processing circuitry, designers have begun to reduce the precision and complexity of conventional integrated analog filter circuitry by creating analog circuits whose outputs are digitized and forwarded to the digital domain in which various complex processing and filtering operations may be performed. Such arrangements are sometimes referred to as mixed-signal integrated circuits.
One area of application for such mixed-signal arrangements is in implementing a complete radio receiver, or at least large portions of a radio receiver, in an integrated circuit. In some radio receiver architectures an incoming RF signal is mixed down to a lower intermediate frequency which is then digitized for further processing in the digital domain. In some instances, control information may be returned to the analog domain from the digital domain.
What is needed are methods and apparatus for converting analog signals to digital signals in a radio receiver channel that are compatible with cost-effective implementations of substantial digital signal processing resources, while preferably moving quantization noise from the analog to digital conversion process out of the frequency band-of-interest, and removing by digital filtering.